1. Field of the Invention
The present invention relates to temperature conversion and, more particularly, to a system for producing high temperatures from sources of relatively low temperature energy sources.
2. Description of the Prior Art
There are many processes which require high temperatures for their efficient operation. For example, for a large number of chemical reactions there is a practical lower limit of temperature, below which a desired reaction will not proceed, or below which it proceeds too slowly to be of technical value. In another example, the efficiency of the process by which electrical power is generated by turbines, driven by vapor, is critically dependent on the vapor temperature. Higher vapor temperatures produce more electrical power output from the same energy content, and permit smaller equipment, at a lower capital investment to be used, compared to those required to generate the same power using lower temperature vapor. Modern turbine-driven electrical generators operate at an input temperature of about 550.degree. C., using super-heated steam. While there are many potential sources of energy which can be used to heat a fluid to produce vapor, most of the economical sources do not provide sufficiently concentrated energy to vaporize a continuously flowing fluid to the desired high temperatures, assumed to be on the order of 500.degree. C. or higher.
For example, while solar energy concentrators of the tracking type are capable of producing vapor at sufficiently high temperatures, such concentrators are very expensive because of the need for tracking mechanisms of substantial accuracy and the need for large and precise energy concentrators, such as parabolic reflectors with associated optics, in order to project a very small concentrated sun image on the collector targets. To date, the less demanding and less costly non-tracking type solar energy concentrators are only capable of producing steam at lower temperatures on the order of 300.degree. C. Geothermal energy can also be used to produce steam or vapor in about the same temperature range of 300.degree. C. Such temperatures are too low for efficient vapor turbine electrical energy generation.
Thus, a need exists for a system and process to recover heat energy from low temperature heat sources and to convert the recovered energy to higher temperatures.